walle prepa was comp MWC MWC cond polym Keyw PAC
nano and s in va incre chara years polym wide draw mate defic
* ) For
Role o modific
Prashant
1 Univers India
2 Univers 160014, I
3 Indian I
Received Abstrac Nano-ind ed carbon n ared by solu varied by positions (0
CNT appro CNTs in b ducted for
mers.
words: Nan CS:62.25.-g,
1. Introd With the otubes (CNT structural pr arious areas easing emp acterization s to make mers and po
Polycarb ely used for wbacks like erial to mak
cient proper
r correspondenc
of carbo cation in
t Jindal1*, M ity Institute o ity Institute o India
Institute of Te
d 3 May 20 ct
dentation te nanotubes-p ution blend
weight fro 0.5%) of M oaching 10%
better load smaller com
no indentati , 68.35.Gy,
duction e discovery Ts) [1-4], w roperties, en s, be it ele phasis on n techniques
composites olycarbonat bonate (PC) r several en low mecha ke compos rties. Apart
ce, E-mail jinda
on nano hardness
Meenakshi G of Engineerin of Chemical echnology, R
13; Revised
echnique ha polycarbona ding followe om 0.5 to 1 MWCNTs a
% as compar transfer pro mpositions
on; compos 81.07.-b, 8
of new Ca which have b ngineering ectronic or
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Goyal2, Nav ng & Techno
Engineering Roopnagar-1
d 22 July 20
as been used ate (MWCN ed by comp
10% in PC and increas red to pure operty. The of carbon
sites; hardne 1.05.Ni, 81
arbon based been found application mechanical nology, wh imension, s nanomateria weight poly applications gth, limit it CNTs, need many other
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vin Kumar3 ology, Panja g & Technolo
40001, Punj
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d for mecha NT-PC) co pression mo C. Hardness
sed to near PC, indicat ese results based nan
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hich has r serious attem als as reinfo ymer which
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ted 3 Augus
anical chara mposites. T lding. The s increased
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are extensiv
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acterization The compo
amount of by 68% f for compos y the effectiv
eement wit s and also
ullerenes an lectronic, m use of these upplemented n extremely been made in matrix o e in bulk fo dability. How
ications. Th enhanceme vely used w
ites for
rh-160014, Chandigarh-
of multi- osites was
MWCNT for minor
sitions of ve role of th studies
in other
nd carbon mechanical
materials d by ever
y unique in recent of various orm and is
wever, its herefore a ent of the with multi-
Prashant Jin
86 wall carb compared propertie use are resilience any exter It is a co comparis nano ind under a p hardness reaching towards i reaches a
T commonl hardness measured R comprisin nylon-6 ( MWCNT and these on them, Few-laye methacry For comp times tha same fac reason fo the prese improve
ndal, et al. / Rol
bon nanotu d to single es [5] which
hardness, e, toughnes rnal abrasio omplicated son to host dentation eq
preset fixed . During th
the fixed its initial po a depth ( )
Fig. 1: Ge The most co ly known a is calculate d indent und Recently, res ng of MW (PA6) hardn Ts by weigh
e static prop however th er grapheme ylate) (PMM positions of an pure PV ctor. Effecti or this impro
ence of MW any static m
le of carbon nan
ubes (MWC walled CN h need to be elastic mo ss etc. Amo on, scratch o
function o matrix grain quipment [6
load value his process, load the in osition. The . Fig. 1 repr
eneral loading ommonly us as Berkovich
ed by H der maximu sults have a WCNTs othe
ness (61MP ht [10]. Low perties also he values w e (FG) rein MA) was als f 0.6% FG in VA. Similar
ive load tra ovement. A WCNTs in mechanical
notubes in poly
CNTs) whic NTs. From
investigate odulus, stre ong these pr or indent be
f the grain n size. A m 6, 7] and ch
for a given the maxim ndenter star e indent in t resents the g
g and unload sed tip is a t h tip [9]. B
, wher um load
lso been rep er than PC Pa) increase wer compos o improved were very m nforcement
so tested fo n PVA, the ly, FG rein ansfer and l
nother expe the polym property. T
ycarbonate comp
ch are also mechanical ed for any m
ess-strain r roperties, h ecomes very size and c measure of h haracteristic n loading tim mum penetra
rts unloadin the sample
general pro
ding flow dur three sided Based upon re is
.
ported perta as host ma ed consisten sitions of M
when other much differe
with polyv or hardness hardness w nforcement larger surfa eriment con mer poly (m The reason s
posites for mod
variants o l engineerin material befo response to hardness res y important composites hardness is cs of an in me are evalu
ation depth ng and mov
starts recov cess of inde
ring Nano-in pyramid sh the labeling the contact aining to sta atrix. When ntly by 85%
MWCNTs als r type static ent due to d vinyl alcoho using nano was found to
in PMMA ce area of nducted by O methyl meth
suggested fo
dification in har
f CNTs bu ng view po ore applying o external
sistance of for static lo tend to mo usually obt ndent forme uated [8, 9]
( ) is c ves away f vering elasti entation on
ndentation pr haped diamo
g as indicat area as cal atic load tes n the host
% when com so showed i c load tests different loa ol (PVA) an o-indenter by o be increas
improved FG has bee Olek et al [1 hacrylate) (P
or this was
rdness
ut much ch oint, some o
g it into pra load, elast the specim oad applica odify the si tained by us ed by a nan to determin calculated.
from the sa ically and fi any specim
rocess.
mond indente ted in Fig.
lculable from sts on comp
consists of mposed of o improved r
were perfo ading direc and poly (m by Das et al
sed by almo the hardne en the sugg 12] observe
PMMA) di that the ind
- heaper
of the actical
ticity, men to
ations.
ize in sing a no tip ne the
After ample finally men.
er tip, 1, the m the osites f neat only 1%
esults ormed ctions.
methyl [11].
ost 1.5 ess by gested d that d not denter
87 displaces the slippery MWCNTs due to which the actual measure was of PMMA matrix only. When the MWCNT composition was increased from 1 to 5%, the hardness still remained unaffected. Further, they coated MWCNTs with silica, this resulted in enhanced hardness for the composite. 4% MWCNT-silica in PMMA measured twice the hardness in comparison to pure PMMA.
Overall, a gradual increase in mechanical properties with increase in MWCNT composition in various types of polymers has been reported over the years.
In this paper, we investigate the effect of varying compositions of MWCNTs in PC on the hardness property which supplements the results of dynamic loading on similar samples reported by us already [13].
2. Sample Fabrication
We procured MWCNTs having diameter about 10-30nm and length 1-10 microns from Nanoshel Intelligent Materials Pvt. Ltd, USA. These were characterized using Fourier Transform Infrared Spectroscopy (FTIR) as shown in Fig. 2. The spectrum shows peaks at 1567cm-1 and 1176cm-1 which are indicative of the MWCNTs.
Fig. 2: FTIR spectra for MWCNTs with peaks at 1567cm-1 and 1176cm-1
We adopted the solution blending method for fabricating composite films of MWCNT-PC [14] and then molded them into desired shape. Pure PC beads of about 1gram were dissolved in a solvent 10ml of Chloroform. The mixture was suspended and stirred to form a clear solution. Then MWCNTs of different weight % of PC were taken and ultrasonically dispersed in Chloroform to obtain stable suspensions. The PC solution and MWCNTs suspensions were then mixed together forming a series of different weight % (0.5, 0.75, 2, 5.0 and 10 wt %) compositions of MWCNT-PC mixtures. These compositions were then again ultra-sonicated to obtain a uniform dispersion of MWCNTs in PC. Thin films of thickness nearly 0.3mm were cast from this solution by pouring the solutions into glass petri dish and allowing the solvent to evaporate for more than 24 hours. These films were then characterized using FTIR. Fig. 3 shows the spectra for pure PC film whole Fig. 4 is the spectra for MWCNT-PC film. In Fig. 4 the peak at 1584cm-1 is visible while there is no such peak in Fig. 3. This peak is indicative of the MWCNTs presence. Scanning Electron Microscopy (SEM) image is shown in Fig. 5 which indicates the presence of randomly oriented MWCNTs in PC base matrix. These films were then separated from the petri dish and one by one broken into small pieces. For each composition, the small pieces were inserted in a small die of the compression moulding machine. After filling the die completely with these small pieces, a plunger was used to manually press a steel plate which
40 45 50 55
0 1000 2000
3000 4000
Intensity
per cm
MWCNTs 1176
1567
Prashant Jin
88 covered After nea finished was extra surface o testing.
ndal, et al. / Rol
the die. Th arly 15 min specimen in acted from of the disc.
Fig. 4: FTI 40
400
le of carbon nan
he die was ns of pressin
n the form the die. Mi After these
F
R spectra for
Fig. 5: SEM 3000 000
3000 00
15
notubes in poly
kept at hig ng, the arran
of a cylind inor finishin e operations
Fig. 3: FTIR
r 10% MWC
M image for 2000 per cm
1 2000 per cm
584
ycarbonate comp
gh temperatu angement w
drical disc o ng operatio s, the discs
R spectra for p
CNT-PC com
r 10% MWC 1000
0 1000
posites for mod
ures to faci was allowed of diameter
ns like buff were ready
pure PC.
mposite with
NT-PC comp 0
20 40 60 80
0
Intensity
0 5 10 15 20 25 30
Intensity
dification in har
ilitate melti to slowly c 10mm and fing were p y to be used
a peak at 158
posite.
Pure PC
MWCNT‐PC rdness
ing of the f cool. Finally d thickness performed o d for indent
84cm-1. C
C
- films.
y, the 5mm on the tation
Tribo for in samp were discu much hardn comp
F
3. Nano Nano-ind oIndentor. D
ndentation ples.
Fig. 6 de e subjected
ussed in Fig h lower than
ness is calcu position inc
Fig. 6: Loadi
Fig. 7: Va
Indentatio dentation te Different co and the res epicts the co to a peak g. 1) for sam
n that of pu ulated. Fig.
creases in PC
ng and unloa
ariation of ha on
ests were pe ompositions sults were t omplete loa k load of 1 mples compr ure PCs. Ba
7 depicts h C.
ading curves
ardness and p
erformed on s of MWCN
then compa ading and un 1000µN. Th rising highe ased on the how penetra
s for various 1000µN
penetraion d
n the above NT-PC com ared to the nloading pro he figure i er amounts equations g ation depth a
composition N.
epth with MW
samples us mposites we indentation ocess for va ndicates th (5% and 10 given by Ol and hardnes
ns under a sta
WCNT comp
sing Hysitro ere used as n results of arious samp hat both , 0%) of MW liver and Ph ss varies as
atic applied l
mposition in P
89 on T1 950 specimen f pure PC ples which
, (as
WCNTs are harr [8, 9]
MWCNT
oad of
PC.
Prashant Jindal, et al. / Role of carbon nanotubes in polycarbonate composites for modification in hardness
-
90
4. Results and Discussion
It is clear from Fig. 7 that hardness increases consistently as MWCNT composition increases in PC. As we can observe hardness for 10% composition in comparison to 5%
composition is only about 10% higher, but for minor compositions like 0.5% to 0.75% this rise is nearly 40%. This means that increase in composition of MWCNTs in PC tends to saturate the hardness effects. Vivekchand et al [15] have shown that MWCNTs enhance the load transfer capability in polymers which results in the enhancement of their mechanical properties. Apart from this, stronger π-π interactions between MWCNTs and the base material and high surface to volume ratio [11] of MWCNTs in base material enhance the overall strength of the composite. So, in this case also MWCNTs play a similar role with PC.
We had earlier investigated [13] the dynamic loading response on similar samples using Split Hopkinson Pressure Bar (SHPB). We had found that for low concentrations of 0.5% MWCNTs, the increase in dynamic strength was most significant while for higher concentrations of 5% MWCNTs, this increase was negligible. At low compositions, proper dispersion of MWCNTs ensured binding the PC with MWCNTs due to which the absorption capacity of the composite surface enhanced. From the results of this paper, hardness number which gives is a measure of local performance was found to be high because short range interactions get enhanced for higher concentrations of MWCNTs. However, apart from hardness other static properties also need to be evaluated to categorically find out the most suitable composition of MWCNTs in PC.
5. Concluding Remarks
This paper presents results of hardness obtained by a nano-indenter on MWCNT based PC composites with varying compositions of MWCNTs. The results indicate categorically that about 5% MWCNTs is sufficient to enhance the hardness of PC by a factor of nearly 4.5 using a simple solution blending fabrication technique. This increase in hardness enables usability of PC for several new applications related to severe loading conditions like stress protective shields, load resisting jackets and covers.
Acknowledgements
Prashant Jindal gratefully acknowledges financial support from the Defence Research Organization (DRDO) for a research project (No. ARMREB/DSW/2011/129).
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